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Adjusted to six positions

Adjusted to six positions
October 14, 2015 Adriaan

Drawing Miyota 9015

All the Eza watches are adjusted in six positions by hand. Adriaan is a certified watchmaker and does all the final checks of every watch himself. When you buy an Eza, you will get a small receipt inside the authentic packaging that shows the exact deviations in seconds per day.

What is the importance of adjusting a mechanical movement in six positions?

When you wear a watch that runs on a mechanical movement, the watch will switch from many different positions during the day. The balance wheel is the part that regulates the precision of the watch. If the balance wheel of an EZA makes exactly 28800 vibrations per hour, the watch will run exactly on time. The centre of gravity in the balance wheel is never perfectly in the middle. When you hold a watch horizontally (dial up or down), the balance vibrates on the tip of one of it’s pivots. The centre of gravity doesn’t influence the movement. When you hold your watch vertically (crow down, up, left or right), the balance wheel will vibrate on the two pivots. In this poristion, the friction will be higher. When a movement runs correctly, the amplitude of the balance wheel will be higher in a horizontal position then in a vertical position.  Besides this, the centre of gravity, which is never exactly in the middle, will start to disturb the vibrations of the balance wheel when the watch is in a vertical position.

When the centre of gravity is, for example, off the middle to the right of the balance wheel. Let’s say that the balance wheel starts turning clockwise. During the first 90 degrees, the point of gravity accelerates the turn. When it passes the lowest point, the point of gravity starts to de-accelerate the balance wheel. If the amplitude of the watch is 270 degrees, the point of gravity accelerates the balance one third of the way and de-accelerates it two third of the way. This is is disadvantageous for the precision of the movement.

By measuring the amplitudes in different positions, the watchmaker can calculate where the point of gravity is. By removing some material form the balance wheel at this point, or adding material on the opposite side, the watchmaker can reduce the off centre point of gravity. After this, the watchmaker can recalculate his adjustment and check if the improvement is enough.

Finally, the watchmaker adjusts the deviations in seconds per day in six positions. It is impossible for a mechanical watch to run perfectly on time. The watchmaker tries to be as close as possible to zero seconds deviation per day. The 1st criterion for the watchmaker is that the maximum difference between all the 6 positions, fully wounded and after 24H running, is 10. After this the deviations in all 6 positions are summed up and then divided by 6. This number has to be between -2 and +8. Every EZA watch is very precisely adjusted and passes these 2 criteria before leaving the atelier.